The Senate passed the budget deal Wednesday, but the House and Senate seemed to switch identities during the budget episode. Some of those shifts might endure, others might be the politics of the moment.

WASHINGTON — Look through the microscope of the just-passed Bipartisan Budget Act, and you’ll see that Republicans in both the Senate and House darted about like protozoa.

A handful of Republican senators who might have normally supported this modest two-year compromise voted against the bill that averts a much-feared government shutdown. In the House, about half the tea party caucus – who normally reject compromise – backed it.

The switcheroo makes it look like the House and Senate are trading places – with the House taking on some of the more “moderate” characteristics of the Senate, and the Senate taking on more of the partisan characteristics of the House.

On the Senate side, that change is visible in the greater influence of the tea party, including the outsized role that freshmen tea party Sens. Ted Cruz (R) of Texas and Mike Lee (R) of Utah played in forcing October’s government shutdown. On Wednesday, all eight senators that identify with the tea party except one, Ron Johnson (R) of Wisconsin, voted “no” on the budget deal, which passed the Senate, 64 to 36.

More noteworthy: Senate Republicans who have been known to work across the aisle might have supported this bill had it not been for the fact that they all face primary challenges next year that test their conservative credentials. Those senators include Lamar Alexander of Tennessee, Thad Cochran of Mississippi, Mike Enzi of Wyoming, Lindsey Graham of South Carolina, Pat Roberts of Kansas, and even minority leader Mitch McConnell of Kentucky.

Each argued vigorously against parts of the budget deal he didn’t like – including changes to military retirement pay and busting current budget caps. But each has also backed “imperfect” legislation in the past and nothing’s to say a problematic provision can’t be reviewed in the future.

Another sign of increasing House-like partisanship in the Senate: the intensified fight over minority-party rights. The minority has basically no rights in the House. Almost everything is done by majority rule and a Rules Committee does leadership’s bidding in limiting amendments and debate in order to make more workable a body of 435 members who directly represent districts all over the country. The tradition of the Senate, whose 100 members serve statewide constituencies that are far more diverse, is more deliberate and slow, with rules that often require a supermajority or unanimous consent to proceed.

When Democrats recently did away with the 60-vote threshold to end debate on most presidential nominees – a pausing and blocking device available to any senator – Republicans retaliated through other procedural means. Last week, the Senate was forced into all-night sessions as business slowed to a crawl.

“If we were to see continued changes to Senate rules that made more and more simple-majority politics, we would see it become more partisan like the House, and we would see less of an ability of Democrats and Republicans to work together,” says Professor Black.

But here's a surprise. The House last week saw far less partisanship than usual. Uncharacteristically, a majority of Republicans voted with Democrats in favor of the budget agreement. Not only that, of the 48 representatives identifying themselves as members of the tea party, only 23 kept in line with that caucus to vote against the deal. That’s a significant shift for a group that marches in formation.

The bipartisan budget deal reflects “lessons learned,” as Speaker John Boehner (R) of Ohio explained on the morning of the vote – painful lessons such as the plummet in GOP approval ratings after the government shutdown in October. And it reflects a readiness to “try to make divided government work,” as House budget meister Paul Ryan (R) of Wisconsin said last week.

But such shifts in institutional character are changes of degree. With a third of the Senate and all of the House facing voters in November, lawmakers are closely tracking the response back home. The mere prospect of a credible primary challenge often fires up deep partisanship.

Julian Zelizer, a congressional historian at Princeton University, cautions that Congress may have passed a bipartisan budget deal, but it comes after a “huge train wreck.” That context is important to remember, he says. Congress isn’t trying to solve big issues like entitlement reform. It is simply avoiding another train wreck. “The question is, can Congress make deals without crises like this."